1. Technical Field
The present invention relates to a thermal detector, a thermal detection device, and an electronic instrument.
2. Related Art
Pyroelectric-type and bolometer-type infrared light detection devices are known thermal detection devices. Infrared light detection devices detect infrared light based on the heat that is produced when an infrared light-absorbing film absorbs infrared light, causing an excitation voltage to be produced in the detection element (pyroelectric-type) or causing a resistance value to change (bolometer-type).
In order to improve sensitivity by increasing infrared light absorption, it has been proposed that the diaphragm that constitutes the infrared light absorbing film be supported on a substrate via a hollow part, where the distance between the infrared light absorbing film and the completely reflective film that is formed on the substrate adjacent to the hollow part is set at λ/4n (λ: infrared light wavelength, n: integer) (see, Japanese Laid-Open Patent Application Publication No. 2000-205944 (FIGS. 2, 3)).
In addition, in order to improve sensitivity by increasing infrared light absorption, a structure has been proposed wherein a plurality of upper infrared light-absorbing layers are disposed, with spatial separation, on a lower infrared light-absorbing layer, with respective reflecting films formed on the upper and lower infrared light-absorbing layers (see, Japanese Laid-Open Patent Application Publication No. 2003-304005 (FIG. 2)).
Moreover, in order to increase detection sensitivity by decreasing loss due to reflection at the infrared light film, it has been proposed that a first infrared light absorbing film be formed on the side surfaces of a V-shaped recess part, and that a second infrared light absorbing film be formed on the bottom surface thereof, so that infrared light that is reflected by one of the first and second infrared light absorbing films is directed to the other infrared light absorbing film (see, Japanese Laid-Open Patent Application Publication No. 07-190854 (FIG. 2)). In patent document 3, the angle of inclination of the V-shaped recess is set so that there are a total of three reflections at the first and second infrared light absorbing films, thereby increasing the number of times the light is incident on the infrared light absorbing film, thus increasing absorption.